Method and apparatus for threading hollow metal articles



Sept. 15, 1936.

METHOD AND APPARATUS FOR THREADING HOLLOW METAL ARTICLES H. A. UNKE v Filed Feb. 18, 1935 3 Sheets-Sheet 1 y n v INVENTOR.

Hee/NA h/KE ATTORNEY Sept. l5, 1936. H, A UNKE 2,054,182

METHOD AND APPARATUS FOR THREADING HOLLOW METAL ARTICLES Filed Feb. 18, 1935 3 Sheets-Sheet 2 INV ENT OR. HEPMHNA fn/(s fir?? Sept. 15, 1936. A UNKE 2,054,182

METHOD AND APPARATUS FOR THREADING HOLLOW METAL ARTICLES Filed Feb. 18, 1955 E/ rl/ \\\l INVENTOR,

/ HERMAN/4. (/NKE 1 M y ATTORN YS Patented Sept. 15, 1936 UNITED STATES METHOD AND APPARATUS FR THREADING HOLLOW METAL ARTICLES Herman A. Unke, Cleveland, Ohio Application` February 18, 1935, Serial No. 7,060

12 Claims.

This invention relates to a novel method and apparatus for rapidly and economically forming threads on the walls of. hollow metal articles.

An object of the present invention is to provide a novel method for threading hollow metal articles comprising the displacing of metal of the wall of the article radially by pressure applied on one side thereof, and in the same operation forming at least a portion of the displaced metal into a continuous solid thread on the other side of the wall.

Another object of the invention is to provide a novel method of. threading relatively thick walled hollow metal articles which comprises displacing metal of the wall oi the article radially by applying pressure on one side thereof and shaping the displaced metal into a continuous solid helical thread on the other side of the wall, and meanwhile supporting the metal of the wall at each side of and immediately adiacent to the metal being displaced.

Still another object of the invention is to provide a. novel method of forming a solid continuous helical thread on a tubular metal article, which comprises shearing and displacing metal of the Wall of the article radially thereof., and in the same operation shaping at least a portion of the displaced metal into a solid continuous thread.

It is also an object of this invention to provide improved thread forming apparatus for carrying out the novel method of -my invention.

Another object of the invention is to provide improved thread forming'appar'atus, of the type referred to, embodying dies of novel construction and also embodying novel means for supportingA and actuating the dies.

Yet another object of this invention is to provide a novel method and apparatus for removing the threaded articles from the dies.

Other objects and advantages of this invention will be a'pparent from the following description when taken in conjunction with the accompanying sheets of drawings, wherein Fig. l. is a longitudinal sectional View taken through improved thread forming apparatus constructed according to my invention.

Fig. 2 is a transverse sectional view taken through the die members, as indicated by line 2 2 of Fig. l.

Fig. 3 is a transverse sectional view taken as indicated by line 3 3 of Fig. 1.

Fig. 4 is a transverse sectional view taken through the driving gearing, as indicated by line d t of Fig. l. f

Fig. 5 is a sectional view illustrating a detail of, construction and taken on line 5-5 of Fig. l.

Fig. 6 is an elevational view with parts broken away, showing the cooperating die members and illustrating the thread forming action thereof.

Fig. 7 is a' partial sectional view, on an enlarged (ci. sir- 6) scala-showing the forming of the thread by the die members in accordance with my novel method.

Fig. 8 is a side elevation of a threaded article produced by my novel method and apparatus.

Fig. 9 is an end view thereof, and l Fig. 10 is a partial sectional view, on an eny larged scale, with the article applied to a threaded member and showing the cooperation between the threads ofthe article and of the member to which it is applied.

In the accompanying drawings to which more detailed reference will now be made, I have illustrated the manner of carrying out my novel thread forming method, and have illustrated one form of threaded article which may be produced thereby. I have also illustrated one form of novel apparatus which maybe used for applying my novel method to the commercial production of threaded tubular metal articles. It will be understood, of course, that various kinds of threaded articles may be`produced by my method, and that that feature of my inventionl which has to do with the adaptation of my method to the commercial production of threaded articles, may be embodied in various kinds of apparatus and machinery.

Before proceeding with a detailed description of my novel thread forming method and apparatus, I shall describe briey one form of tubular metal article vwhich can be readily produced by the use of that method and apparatus. The article illustrated in this instance is a thread protector intended for use onthe ends of pipes, or other threaded members, and is more fully disclosed in copending application, Serial No. 717,-

635, led March 27, 1934. It will be understood,

of course, that the specic form of threaded article here referred to, is merely in illustration of the method and apparatus of my invention, and that the invention may be applied to the proy duction of numerous other threaded metal articles.

As shown in Figs. 8, 9, and 10 of the drawings, the thread protector l5 referred to in this instance, comprises a. relatively thick Walled metal sleeve, such as might be formed by suitably drawing or shaping a sheet vmetal blank in appropriate dies. thereof,- in this instance on the inside, with a continuous solid helical thread i6, which is formed, at least in part, from metal displaced substantially radially inwardly, of the wall of the sleeve. Such displacement of metal to form the solid thread leaves a helical groove il in theouter surface of the sleeve.` The Yhelicai thread it is of V-like form, as shown in Fig. l0, and engages in adjacent convolutions ci the thread groove it of a pipe end I9 or other threaded member to The metal sleeve is provided on one side '50 which the article is applied.. The helical thread I6 may comprise any desired number of convolutions, and in this instance, forms a threaded section'intermediate the ends of the tubular metal article. l

One end of thethreaded article I5 is open so that the article may be readily applied to the end of a pipe or other member and screwed onto the threads thereof. The opposite end of the article has an integral inwardly extending flange which is adapted to engage the end portion of 4 the pipe or threaded member with a locking acodand apparatus for removing the threaded articles from the dies, as will be explained more fully hereinafter.

As mentioned above, my novel method contemplates forming a solid continuous helical thread on one side of the wall of a tubular metal articl'e, by displacing metal radially of the wall and shaping at least a portion of such displaced metal to form the solid helical thread. My novel method also contemplates the supporting of the metal of the wall at spaced points and the application of pressure to the opposite side of the wall at points intermediate the points of support, whereby the metal of the wall is subjectedto a shearing action which displaces metal substantially radially to form the continuous solid helical thread. Y l

I am aware that it has been proposed heretofore to form threads on tubular metal articles by cooperating die members, but in all cases of which I am now aware the forming of the threads was accomplished by a deflecting or bending of the metal of the wall of the article. Threads can be formed in this manner on relatively thin walled articles, but the threads are not solid threads nor are they of a desired V-like shape. Furthermore, attempts to form such threads on relatively thicker walled articles by a deecting or bending of the metal has resulted in threads of unsatisfactory character and has resulted in excessive strains and wear on the thread forming dies.

In accordance with my novel method, metal of the wall of the tubular article is actually sheared and displaced transversely of the wall, and at least a portion of the displaced metal is shaped into a solid, continuous helical thread. The thread thus formed is of a desired V-shape, and is also very strong and rugged as compared with the hollow threads formed by deflecting or bendlcontinuous helical groove 28 formed therein, and

one or more die rolls 21 which are the same diaxneter` as the mandrel and are disposed adjacent thereto. The rolls have' on their outer surface aridge or'rid'ges in opposed relation to' the y helical groove 26.

The ridge or ridges of the die rolls 21 are pref- .erably arranged to form a helical thread 28 which is of opposite hand to` the helical thread of the mandrel. As shown in Figs. 6 and 'I the consecutive convolutions of thethread 28-of each'roll lie opposite the consecutive convolutions of the thread groove of thelmandrel, and where the article I5 is to have an internal right hand-thread the mandrel is provided with a right hand thread groove and the roll 21 is provided with a left hand thread ridge 28. In this instance, I have shown three die rolls 21, spaced at equal intervals circumferentiall'y around the mandrel 25, but any desired number of such rolls may be employed.

As best shown in Fig. 7 of the drawings, the

helical groove 26 ofthe mandrel 25 has tapered side walls 29 which converge to provide the groove with a V-like bottom. Outwardly of the convertially parallel side faces or walls 30. The groove 26 is formed in the surface 0f the mandrel so as to leave upstanding spiral ridges or lands 3l between adjacent convolutions of the groove. The tops of these ridges or lands are at or square, as shown in Fig. '1,'andl have supporting engagement with the inner surface of the tubular metal arv ticle I5 when the latter is applied to themandrel.

'I'he thread 28 of the die roll 21 has the same pitch as the thread of the mandrel 25, and hence the adjacent convolutions or ridges thereof are spacedl apart a distance corresponding with the spacing or pitch of the adjacent convolutions of the groove 26. The convolutions of the thread 28 also have flat or square tops of substantial width, similar to the lands or ridges 3I of the mandrel. The ridges ofthe die roll are preferably somewhat narrower than the width of the groove 26, although the proportions of the ridges and grooves may be varied in accordance with the characteristics of Ithe thread to be formed and also in accordance with the characteristics of the metal to be Worked. The purpose of the ridges gently tapered wall 2'9, the groove 26 has substan- 28 is to force metal of the article I5 in a direction transversely of the wall thereof and into the convolutions of the helical groove 26. In accomplishing thisv function vthe ridges 28 cooperate with the wall of .the article at each side of and immediately adjacent to the metal being displaced by the ridges 28. In Fig.'7 of the drawings I showthe lands 3| in such supporting relation `with thf wall of the metal sleeve, and it will be seen that as the displaced metal is shaped into the V-like thread I6, the square tops of the lands also serve to formv the square recess 3|' at the bottom of" the thread groove. This square recess is desirable in the article I6 because it provides a clearance spaceffor the top edge of the thread to which the article is applied and prevents dulling of the thread.

Although my novel method for threading hollow .p metal articles may be carried out with various kinds of machinery and apparatus, as mentioned above, I have devised novel apparatus with which this method can be carried out especially well. This apparatus .may include a support or frame 36 which may be mounted upon a suitable bed or l foundation I6. The frame may have an enlarged portion 31 adjacentwhich the dielmembr rs are arranged, and another enlarged portion 38 adjacent which the driving gearing may be arranged. The enlarged portion 31 is provided with substantially radially extending guide-ways 39 which correspond in number and spacing with the number and spacing of die rolls 21 to be employed. Bearing members, preferably in the form of metal blocks 40, are mounted for radial sliding movement in the guide-ways 39, and are normally urged radially outwardly within the guideways by means of springs 4|. ranged on studs 42 which are carried bythe bearing members and extend outwardly through the cover plates 43, the springs being disposed between the heads of the studs and the cover plates.

A spindle 45 is rotatably mounted in each of the bearing blocks 4, with the ends 46 and 41 thereof extending in opposite directions beyond the bearing member. The end 46 of the spindle extends in adjacent relation to the mandrel 25 with its axis substantially parallel to the axis of the mandrel. The oppositely extending end 41 of the spindle projects through a radially elongated slot 48 of the frame portion 31. The projecting portion 46 of the spindle may be provided with a' threaded section 49 at its outer end and with successive shaft portions 50 and 5I. The shaft portion 50, is of smaller diameter than the portion of the spindle which is journaled in the bearing block 4U to provide a shoulder 52 on the spindle, and similarly the shaft portion 5I is of smaller diameter than the shaft section 50 to provide a second shoulder 53 outwardly of the lshoulder 52. The die rolls 21 are mounted upon the projecting ends 46 of the spindles by being keyed to the shaft sections 5| so as to be driven by the spindles. 'I'he rolls are` retained on their respective spindles by means of bushings 54 which are disposed on the shaft sections 5l, so that the bushings and the rolls are clamped between the shoulder 53 and a nut 55 applied to the threaded outer section 49 of the spindles.

The mandrel 25 may be supported Afor cooperation with the die rolls 21 by a shaft 6B, which is suitably journaled in the frame 35 with an end 6i thereof projecting outwardly from the frame member in substantially parallel relation with the spindles 45. 'Ihe mandrel 25 is keyed, or otherwise connected, to the shaft end 6I so as to be rotated thereby. Provision may be made for axial movement of the mandrel; for a purpose to be presently explained, by arranging the shaft Bil for axial movement in the bearings 62, or preferably by providing a spline connection between the shaft end 6| and the mandrel 25, whereby the mandrel is axially shiftable on the shaft while it is being driven thereby.

When one of the metal articles l5 is to be i threaded, the tubular blank for the article is telescoped over the mandrel 25 and the spindles 45 are then moved 4substantially radially inwardly with respect to the axis of rotation of the shaft to cause the ridges 28 of the'die rolls 21 to I engage theA outside of the metal sleeve and to displace metal from the wall thereof into the helical groove 26 to form the' continuous solid thread on the article. During such inward movement of the die rolls 21 the spindles supporting the rolls are maintained in proper relation with respect to the axisof the shaft 60 by the sliding bearing `memberslll in which the spindles are mounted.

For moving the spindles toward the shaft 60 to press the die rolls 21 against the metal sleeve, as just explained, various arrangements of apparatus may be employed. I prefer, however, to use These springs may be ar suitable cam means for this purpose, and one cam arrangement is shown in the drawings wherein an annular member is disposed around the die rolls 21 and carries cam members 66 and 61 for causing the desired actuation of `the die rolls. The annular member 65 may be supported for rotation by a pair of flanged rollers 61', which are rotatably mounted on the frame. These flanged rollers aredisposed in laterally aligned relation, as shown in Fig. 2, and are spaced apart a distance such that the annular member will be directly supported on these rollers and will be confined to the desired path of rotation by the flanges of the rollers. l

The cam members 66 and 61 are arranged within the opening of the annular member 65, as shown in Figs. l and 2, with the cam members 66 extending in a circumferential series adjacent one end of the annular member and the cam members 61 extending in a circumferential series .adjacent the opposite end of the annular member.

The cam members 66 and 61 correspond in number with the die rolls 21, and in this instance there are three cam members in each circumferential series. form a substantially complete ring, the outer surface of which engages the inner face 68 of the annular member 65. The cam members of the two series are in edge to edge engagement with each other, as shown in Fig. l, and may beretained in the opening of the annular member 65' I bers and the ring member 65 may be prevented 'by onel or more dowel pins il which extend through the iianges 69 and 10 and through the cam members.

The adjacent end faces vof the cam members 66 and 61 have recesses formed therein and which` register to form an annular groove 12 when the die members are assembled in the annular member 65. This annular groove accommodates the outer portion of die rolls 21, while the cam faces of the membersv66 and lform annular cam surfaces 13 and 14 at each side of the annular groove 12. friction roller 15, which is rotatably mounted on the bushing 54 of the shaft section 5| of the spini die, and the cam surface 14 cooperates with a similar roller 16 rotatably mounted on the shaft section 50 of the spindle.'

As mentioned above, the cam members 66 and 61 are provided in number to correspond with the number of die rolls 21-, and in order to have substantially simultaneous actuation of all of the die rolls, these cam members have cam surfaces of substantially identical contour. In Fig. 2 of The cam members of each series 1 The cam surface 13 cooperates with an antithe drawings the direction of rotation of the annular member 65 is indicated as being clockwise, and the antifriction rollers 15 and 16 of the spindles are shown as being at the starting points of the respective cam members. When the annular member 65 has been rotated throughV an angular distance to bring the elevated cam portions 11 Vinto engagement with theA antifriction rollers, the spindles are shifted inwardly toward to some extent the thread portions formed by the preceding die roll, so that the thread portions formed by each roll willmerge with and' .be a smooth continuation of the thread portions formed by the preceding roll. The elevated cam portions 11 are followed by relatively depressed cam portions 18 which allow the spindles 45 to be moved outwardly with respect to the shaft 88 by the springs 4|. Such outward movement of the spindles causes the ridges of the die rolls 21 to be disengaged from the work to permit removal of the latter from the mandrel 25. During the action of the cam members, as just described, the annular member 85 rotates for one-third of a revolution, that is to say 120, which causes one p set of cams 6G and l81 to act on and travel past one of the die rolls 21. During this same period I of time, that is while thev annular member 85 makes one-third revolution, the mandrel and the die rolls 21 each make two revolutions.

Since the groove 28 of the mandrel 25 is a spiral groove, it is necessary to have the die rolls 21 keyed to their driving spindles 45 so that the ridges-28 of all ofthe rolls will be opposite the convolutions of the groove 28 of the mandrel.

With the ridges and grooves of the rolls and mandrel in this relation, the ridges of the rolls will follow the grooves of the mandrel as the rolls and' mandrel are rotated, and inso doing, will form the desired threaded section on the article. In arranging the rolls 21 in proper relation to the f thread grooves of the mandrel, it may be desir- /able to insert shims 18, of proper thickness, be-

tween one or more of the rolls and their clamping shoulders 58.

The mandrel 25 may, as mentioned above, be splined to the shaft portion 8| so as to be adjustable thereon. and for adjusting and holding the mandrel in proper relation to the rolls 21 without the need of reaching into the recess of the annular member 85 with tools, I provide the mandrel holding and adjusting bracket 88. This bracket extends into the recess of the annular member 85 and has a fork portion 8| engaging -in an annular groove 82'of the mandrel.. The bracket- 82 may be mounted for sliding movement on a guide rod 88, which is disposed below` the shaft 88, with its axis extending substantially parallel to the axisn of the shaft. l

The bracket 88 may be normally held against movement on the rod 88 by means of a cam or bushing 84 having operative connection with the bracket. The bushing 84 is mounted o n a drive shaft 88 and has an annular groove 81 in its outer surface. v The shaft 88 may be suitably journaled A in the brackets 88' and 81' of the machine frame.

The bracket 88 mayhave an enlarged bearing portion 88 which is journaled on the bushing 84 and which has a roller 88, or the equivalent, arranged to operate in the groove 81. The roller 88 may be mounted on a pin 88"', which is screwed into a threaded opening 88b of the bearing portion 88 as shown in Fig. 5,"or the roller may be otherwise suitably mounted on the bearing'portion. l

mandrel and the rolls 21, such as when the latter are narrower than the section to be threaded on ,v the article or when the ridges of the rolls are parallel to each other instead of in the form of a helical thread, the groove V81 may be shaped to cause any desired extent of such axial movement of the mandrel. Usually, however, the groove 81 is a circular groove, as mentioned above and when vit is desirable to adjust the mandrel axially with respect' to the rolls 21, such adjustment is made by shifting the bushing 84 along the shaft 88. For this purpose I mount the bushing on the. shaft 88 between the nuts 84' of the latter. By adjustment of these nuts, the bushing can be adjusted along the shaft 88 and clamped at a point cor-l responding with a desired adjustment of the mandrel 25. i.

For driving the die rolls 21 and the mandrel 25, and also, if desired, the shaft 88, in timed relation to cause proper cooperation between the rolls and mandrel to form the threads on the article, I provide a common source of power for driving these various parts. AIn this instancel the power source is represented as being a flanged head 88, which may be the flanged end of la power shaft, the head of a lathe or any other suitably driven power member. The shaft 88 hasdirect driving connection with the head 88, and in this instance, such direct driving connection is established through a gear 8| which is'pinned or otherwise connected to the extension 82 of the shaft 88,

these spindles. ,In this instance the flexible dri v` ing means consists of a flexible shaft 85 for each spindle. This flexible shaft may comprise an extensible intermediate portion 88 and universal joints 81 and88 which are connected, respective-l ly, to the spindle portion 41 and to a stub shaft or spindle 88 whichis journaled in, and extends through, the frame portion. The extensible Vand is also connected as by dowel pins 83 or the intermediate part of the flexible shaft 85 may be formed by telescoping shaft sections of the universal joints 81 ,and 88 which shaft'sections are drivingly connected by a pin and slot connection |88 or the like. Rotation is imparted to the flexible shafts .85 by pinions |8| which are pinned or otherwise secured to the spindles 88 and which mesh with the gear 8|.

To provide a suitable power take-off for driving the annular member'85 and-the cam shaft 88 in properly timed relation to each other and to the shafts 8 8 and 85, I may employ a ring gear |88 which is arranged formovement relative lto the driving head 88. This ring gear has internal teeth |84 which mesh with the pinions I8| and external teeth-|85 which mesh withv the gear |88 of a counter-shaft |81. To permit'movement of the ring gear |88, relative to the head 88, I connect the ring gear toa supporting member |88 which is rotatably mounted on the flange of the head and retained thereon by the plate member Y the frame 35 and has a gear ||0 secured thereto which meshes with an external ring gear H2 to cause rotation ofthe annularmember 65. The ring gear I|2 may be formed on the annular member itself, or, 'as shown in Fig. 1, may be secured to the annular member by suitable bolts IIS.

Rotation may be transmitted to the cam shaft 36 through a gear train consisting of gears IIS, IIB, III and H8, and a counter-shaft IIS upon which the gears IIS and III are mounted. The shaft I I9 may be. suitably journaled in the brackets 86' and 8i below the shaft 86, as shown in Figs. l and 3. The gear I l5 is an idler, which is journaled on the shaft 86 and transmits motion to the gear |66', the latter being keyed to the shaft I I9. The gear I I 'I is also keyed to the shaft I I9 and transmits rotation from this shaftv to the gear I I8 which is keyed to the shaft 86.

From the driving arrangement just described it will be seen that when the head 9i) is rotated it Will cause the shaft G5 to be directly driven at a corresponding speed, and will also cause the die rolls 2l to be driven through the gears IIiI andA the annular member 65, rotation will also be imparted to the shaft 86 and the cam or bushing t5 thereon.

In the operation ofthe apparatus the operator places a sleeve-like metal blank on the mandrel 25, and by means of 4a. suitable clutch or other control (not shown), starts rotation of the driving head 90. Rotation is imparted to the' mandrel, the die rolls 2I, the cam-carrying annular member 65, and the bushing 8d in the manner just explained, which causes the cam rolls 2l to act on the work and cooperate with the mandrel 25 to form the solid continuous thread onthe article. When the die members have traveled through the desired relative movement, as explained above, the apparatus is brought to a stop by either manual or automatic operation'of the clutch and the threaded article may then be removed from the mandrel. I

Since the metal, which is displaced from the wall of the article in forming the thread thereon,

is pressed into the helical groove of the mandrel,l

it will be seen that' it is usually necessary to rotate the article relative to the mandrel in order to remove the same. lThis rotation may be accomplished as a hand operation by the operator, but I prefer to provide power means for this purpose. Such power means is shown in Fig. 1 of the drawings and may comprise an axially movable spindle 625, which is mounted with its axis in substantial alignment with the axis of the shaft 60. A die'orv gripping device |25 of appropriate construction is provided at the inner end of the spindle for gripping cooperation with the threaded article I5. Such gripping cooperation may be obtained by forming a part of the gripping device so that it will enter the out-of- :round opening of the end flange 20 of the ratus, the operator closes a switch in the power circuit of the motor |21 as soon as the threading of the article has been completed. This causes the motor |21 to drive the spindle |25 through the shaitl |28 and the speedreducer |29, and results in the spindle |25 beingmoved `toward the shaft 60 to bring the gripping device I26 into engagement with the article, whereupon the spindle |25 rotates vthe article in a direction to unscrew the same fromthe mandrel 25. The operator then manipulates the control switch for the motor I2'I to reverse the direction of rotation of the motor, thereby causing the spindle |25 to move away fromthe shaft 60 and to carry the article I5 in the same direction. When the article has been moved through a sumcient distance to clear the annular member 65, the motor circuit is opened and the motor -is suddenly brought to a stop by substantially simultaneous operation of a magnetic brake |30. Thesudden stopping of the motor and of the spindle |25 by the action of the brake |30, causes the article I5 to be subjected to a sudden jar which shakes the article loose from the gripping device |26. Thereupon the articledrops in a chute or 'receptacle suitably arranged to receive it.

From the foregoing description and .accompanying drawings it will Vnow be readily understood that I have provided a lnovel method for rapidly and economically producing threaded tubular metal articles. As formed by my method these articles have Aa continuous solid helical thread which is very strong and rugged and of desired accuracy and uniformity. In accordance with my method the solid continuous thread is formed by a shearing and displacing of metal of the wall of the article radially thereof and a shaping or swaging of at least a portion oi the displaced metal into the desired solid continuous helical thread.

It will also be understood from the foregoing description and accompanying drawings that I have provided novel apparatus for producing metal articles having a solid continuous helical thread, although the method of my invention may be carried out with this and various other apparatus and machinery. While I haveV illustrated and described the method and apparatus of my invention in a somewhat detailed manner, it should be understood, however, that I do not wish to be limited to the precise steps of procedure and details of portion of the displaced metal into a continuous,

solid thread on the other side of said wall.

2. The method of forming a solid continuous helical thread on a tubular metal article which comprises rolling a continuous groove in the. article and thereby shearing and displacing metal of the wall of the article only radially thereof and in the same operation shaping the displaced metal into a' solid continuous thread. 3. The method o! threading tubular metal articles which comprises applying pressure on wall is sheared and displaced in a radial direction-v only, and in the same operation shaping at least a portion of the sheared metal into a solid continuous thread. i

4. The method of threading hollow metal articles which comprises applying radially acting pressure to one side of the wall of an article at a plurality of areas lying substantially opposite consecutive convolutions of a helical groove of a die disposed on the reverse side of said wall and meanwhile supporting the Wall on said die at each side of said areas whereby metal of the wall at said areas is sheared and displaced radially only of the article into the die groove and in the same operation is shapedinto a continuous solid helical thread.

5. The method of forming a helical thread on the wall of a tubular article which comprises pressure rolling the wall of the article between cooperating rolls, one of which has a helical land of opposite hand to a helical land on the other roll with the convolutions of the land substantially opposing the convolutions of the helical groove of said other roll, and thereby causing the land of one roll to shear and displace metal from said wall radially only thereof into the helical groove of the other roll while the land of said other roll supports the Wall at each side of and adjacent to the metal being displaced, and in the same operation swaging the displaced metal into a solid continuous substantially V-shaped helical thread.

6. 'I'he method of threading tubular metal articles which comprises applying pressure to opposite sides of the wall of a tubular blank by cooperating die members, one of which has a helical land with an intervening helical groove and the other of which has a helical land of the opposite hand with the convolutions thereof disposed lsubstantially opposite the convolutions of said groove, and causing relative rotary move-` displaced.

7. In apparatus of the character described the combination of. inner and outer die members adapted to receive therebetween the wall o! a vhollow article to be threaded, one of said die members having a helical groove therein and an intervening helical land for supporting engagement with one side of said wall, and the other die member having a ridge disposed opposite said helical groove, means forcausing relative rotary movement between said die members, and

means for pressing saidmembers toward each other, said land and ridge each having a contact face of substantial width whereby the ridge when pressed into the wall pushes metal thereahead relative to metal adjacently supported by the land.

8. In apparatus of the character described the combination of inner' and outer die ,members adapted to vreceive therebetween the wall of Ia hollow article to be threaded, one of said diemembers having a helical groove therein and an intervening helical land for supporting engagement with one side of said wall, and the other die member having a ridge disposed opposite said helical groove, said ridge having a contact face of substantial width for engagement with the other side of said wall, means for causing relative rotary movement between said die members, and

` means for pressing lthe die members toward each other, whereby the relatively wide contact face of the ridge partially shears the wall of the article and pushes metal thereof into said groove.

9. In apparatus of the character described the combination o`f cooperating inner and outer die rolls adapted to receive therebetween the wall of a hollow article to bev threaded, one of said rolls having a helical groove therein and a helical land for supporting engagement with portions of one side of said Wall, and the other roll having a helical land of opposite hand for engagement with the opposite side of said wall at points substantially opposite the convolutions of said groove, means for causing relative rotary movement between said rolls, and means for meanwhile pressing said rolls toward each other, said helical lands each having a contact face of substantial width.

10. In apparatus for threading relatively 'thick walled hollow metal articles the' combination of inner and, outer die members having cooperating continuous helical shear elements thereon, means for causing relative rotary traversing movement between said die members, and means fo'r meanwhile pressing said die members toward each other whereby metal is sheared and displaced substantially radially of said wall to form a continuous solid thread thereon, said shear elements each having a substantially fiat contact face of substantial width.

11. In apparatus for threading hollow metal articles the combination of a mandrel having thereon a helical ridge and an intervening helical groove, and a die roll adjacent the mandrel and having a ridge thereon disposed substantially opposite said helical groove for shearing cooperation with said helical ridge, the ridges ot said die roll and 'mandrel having substantially flat contact faces of substantial width for engagement with opposite sides of the wall of the article.

12. In apparatus for threading hollow metal articles the combination of a support, a die manbers on each spindle at each side of the die roll thereon, and rotary cam means having an internal clearance recess for said die rolls and cam.

surfaces at each side of the clearance recess for cooperation with said anti-friction members.

minnaar:ILUNKE.` 

